Clutch piston safety valve



`I-une 23, 1953 G. E. FLINN 2,642,344

CLUTCH PISTON SAFETY VALVE Filed Dec. 9, 1948 Patented June 23, 1953 CLUTCH yPls'roN SAFETY VALVE f George E. Flinn, Muncie, Ind., assignor to Burgf Warner Corporation, Chicago, Ill., n, .corpora- .tion of Illinois Apsueationnecembers, 1948, serial No. 64,361

My invention relates to fluid pressure actuated friction clutches and more particularly to the fluid pressure responsive piston mechanism for actuating the clutches.

In the past, difficulty has been had with clutches actuated by a fluid pressure responsive piston in that the fluid retained "in the cavity for the piston, when the supply of fluid to the piston was cut oil, Was 'effective due to the 'centrifugal force acting on this residual fluid to cause engagement of the 'clutch when no en-l gagement was desired. y'

It is an object of the invention -to provide an improved clutch piston arrangement which allows the release of the residual fluid remaining in the bore for the piston when the fluid 'supply is cut off. It is a more specific object to provide a valve for opening and closing a 'relief passage which is responsive to the fluid 'pressure supplied to the bore for the clutch piston, so that the valve is closed when clutch engaging fluid pressure is supplied to the piston Vbut is otherwise open.

It is a further object of the inventionto provide a clutch piston arrangement kof the character set forth above which operates during 'actual clutch disengagement to apply "a charge of lubricant directly onto the clutch plates. Therefore, upon each complete cycle of clutch engagement and disengagement, thorough lubrication of the clutch plates is attained. y

The invention consists of the novel l"construetions, arrangements and devices to be hereinafter described and claimed for carrying out the above-stated objects and such other objectsas Will appear from the following description fo'f a preferred embodiment of the invention illustrated with reference to the accompanying drawing, wherein: n

Fig. 1 is a fragmentary,section'al view through a multiple plate friction clutch and piston 'arrangement for applying the same illustrating the principles of the invention; and y Fig. 2 is a sectional view taken on line y'-2---2 vof Fig. 1.

Like characters of reference designate Alike parts in the several views.

Referring now to the drawing, a Vmultiple plate clutch Ill is provided lfor connecting a member II with a shaft I2. The 'shaft I2 is in the form of a sleeve and is rotatably disposed on acentral shaft I3. The member II is also rotatably disposed with respect to the shaft i3 by means of a hub I4.

The clutch comprises interleaved clutch discs 4 claims. (01.121438) the drum I1.

I5 and I5. The clutch discs I5 are splined on the element II, and the clutch discs I6 are splined on a drum I'I lwhich in turn is splined on-'the shaft I2. A backing plate I8 is fixed within the drum I'I, and a piston I9 is provided for compressing the discs between it and the backing plate I8 for engaging the clutch.

The piston I9 is of cylindrical design and isslidably disposed within an annular bore 20 provided inthe drum I1. Fluid under pressure from any suitable rsource may `be induced into the space existing in the-bore '20 at the forward side of the piston ISlby means of a `conduit v2| which communicates with a passageZ Ia which in turn communicates with the space 2lb vexisting between the shafts I2 and I3. The space 2lb communicates withl a lpassage 2Ic vextending through the rshaft I2, whichv passage in turn communicates with an inlet port 2Id provided in A springl 23 is provided between the piston I9 and a retainer ring 24 which -is fixed with respect to the drum I1. The spring 23 yieldably holds the piston I9 in its clutch disengaged position in which it is illustrated.

The piston I9 is provided with an internal cylindrical cavity 25, and a piston 26 is slidably disposed in the cavity'. The ycavity 25 is closed on-its outer endby means of 'a plug 2'1. The plug has a central bore 28 which is in communication with a Vfluid passage 29 extending'through the piston I9 and the plug from one'side to the other. The passage 29 is adjacent the outer periphery of the bore '20 as will be noted. The piston 26 has a stem 30 extending into the bore 28, and a spring 3| is provided for yieldablyholding the piston 26 in itsillustrated position in which it opens the passage l29 .from one side of the piston to the other. Apassage 32 'isp'rovided in the piston I9 connecting the inner end yof the cavity 25 with the bore 20 for purposes :hereinafter to be described. The plug 21 .is fixed yin the cavity 25 by means y'of va pin 33 extending through the piston I9 and into a groove 34 .in the plug.

`The particular lconstruction illustratedtin connect'ion with the clutch IIJ and itspiston I9 is one shown in a prior application of Donald W. Kelbel, Serial No. 793,006., and it will vbe understood that many other different constructions in lieu of the one illustrated may be used in connection with the piston I9. In the illustrated construction, whenr fluid under pressure is applied through the conduit .2| within they bore 20, it moves the piston 'I9 to the left l'as seen in Fig. T1 against the action -cilthe 'spring 23 to yengage the 3 interleaved clutch discs l5 and I8 with each other.

However, it will be noted that the clutch spring 23 is much larger and hence much stronger than the valve spring 3l. Furtherl it will be noted that the piston I9 is normally held in a position wherein its flat end surface is in conforming contact with the ilat end surface of the bore 2D so that communication between the passages 2id and 29 is cut off until the piston I9 has been moved initially by iluid pressure acting on the radially inward piston surfaces which do not engage the wall of the bore. Therefore, it is readily apparent that fluid-pressure introduced through the passage 2|d will enter the passage 32 and fully actuate the valve piston 26 against the bias of the light spring 3l to close the passage 2S by means of the stem 3 before the pressure acting on the small area of the radially inward surfaces of the clutch piston I9 becomes great enough to aetuate the clutch piston against the bias of the much stronger clutch spring 23. In other words, the inherent operation of the construction shown is the initial actuation of the valve piston 25 and then subsequent actuation of the clutch piston i9 as the fluid pressure increases.

The fluid under pressure Within the conduit 2| is released t allow the spring 23 to move the piston l' back into its clutch disengaged positon in which it is illustrated. Under these circumstances, a certain residual amount of fluid would remain in the bore 2e and behind the piston i9, were it not ,for the passage 29 provided to eiiect its release, and when the drum Il and piston I are rotating at high speeds, the centrifugal force on the fluid would move the piston le in the bore 20 to the left as seen in Fig. 1 to engage the clutch I0 at a time when actually no engagement is desired. The piston when the fluid pressure is relieved in conduit 2l moves inwardly in its cavity 25 against whatever centrifugal force may be acting on the piston under tne action of the spring 3| to open the passage 29 and whatever fluid there is in the outer portion of the bore 2E) may escape through the passage 29 to the other side of the piston le, so that the uid is not present in the bore 2s adjacent its outer periphery to cause this undesired engagement of the clutch I8. Such passage of fluid to the rearward side of the piston serves to deposit a charge of lubricant directly onto the clutch plates I5 and i6 each time the complete clutch engaging and disengaging cycle takes place.

I wish it to be understood that iny invention is not to be limited to the specific constructions, arrangements and devices shown and described except only insofar as the claims may be so limited, as it will be apparent to those skilled in the art that changes may be made without departing from the principles of the invention.

I claim:

1. In a hydraulic system, in combination, a rotatable member having a hollow bore, a piston in said bore, means for supplying fluid under pressure into said bore and including a conduit connected with the bore substantially at its inner periphery, said piston being provided with a fluid discharge opening therein adjacent its outer periphery for releasing iluid within the bore so that uid under centrifugal force in the bore will not be eiective to move the piston when no uid is supplied through said cond uit to said bore, a valve carried by said pistonv and effective for opening and closing said discharge passage and responsive to the fluid pressure Within said conduit, and means acting on said valve to prevent movement of the valve due to centrifugal force.

2. In a hydraulic system, in combination, a rotatable member having a hollow bore, a piston in said bore, means including aconduit for supplying fluid under pressure into said bore at the inner periphery of the bore for moving said piston, means forming a fluid relief passage in said piston adjacent its outer periphery so that fluid under centrifugal force in said bore will not be effective toY move the piston when no Huid is supplied through said conduit, and a valve in said piston for opening and closing said fluid relief passage and in communication with the fluid in said conduit so that said fluid relief passage is closed when fluid is supplied to said bore through said conduit, and a spring elective on said valve for counteracting centrifugal force on the Valve to yield-ably hold it in its iiuid relief passage opening position, when no luid is supplied through said conduit.

3. In a hydraulic system, in combination, a rotatable member having a hollow bore, a piston in said bore, said piston being provided with a iiuid discharge passage therein adjacent its outer periphery, a fluid pressure responsive valve carried by said piston and eiective lor opening and closing said discharge passage, and means including a conduit for supplying fluid under pressure for operating valve and ior operating said piston, fluid discharge passage being effective to release duid within said bore through said piston so that fluid under centrifugal force in the bore will not be eli'ecti've to move the piston when no fluid is supplied to said bore, said piston when not operated being substantially ush with said bore and said conduit being connected with said bore and said valve radially inwardly of said discharge so that the fluid pressure suppiied by the conduit rst moves the Valve to a discharge passage closing position and thereafter operates Said piston whereby fluid pressure in said bore built up by centrifugal force is ect-ive to hold said valve in said discharge p age closing position upon release of the preN re fluid from said bore through said conduit, and means acting on said valve to prevent movement oi' the valve duc to centrifugal force.

4. In a hydraulic system, in combination, a rotatable member having a hollow bore, a ton in said bore, i piston boing provided with a fluid discharge passage therein adjacent its outer periphery, a fluid pressure responsive valve carried by said piston and effective for opening and closing said discharge passage, means including a conduit for supplying fluid under pressure for operating said valve and for operating said piston, said uid discharge opening being eifective to release fluid within said bore through said piston so that fluid under centrifugal force in the bore will not be effective to move the piston when no fluid is supplied to said bore, said piston when not operated being substantially flush with said bore and said conduit being connected with said bore and said valve radially inwardly of' said discharge passage so that the fluid pressure supplied by the conduit first moves the valve to discharge passage closing position and thereafter operates said piston whereby fluid pressure in said bore built up by centrifugal force is ineffective to hold said valve 5 in said discharge passage closing position upon release of the pressure uid from said bore through said conduit, and a spring effective on said valve for oounteracting centrifugal force on the valve to yieldably hold it in a uid discharg passage opening position.

GEORGE E. FLINN.

References Cited in the le of this patent UNITED STATES PATENTS Numbex` Name y Date 644,749 Wiehl Mar. 6, 1900 Number 10 Number Namek Date Y Doran June '1, 1938 Kegresse Jan. 20, 1939 Tedden et al. Oct. 31, 1939 Hale June 17, 1941 Advey Jan. 30, 1946 McNairy Feb. 22,1949 McLean Jan. 20, 1950 FOREIGN PATENTS Country Date` Germany Feb. 15, 1924` Germany Mar. 25, 1937 

